Rotaviruses Associate with Cellular Lipid Droplet Components To Replicate in Viroplasms, and Compounds Disrupting or Blocking Lipid Droplets Inhibit Viroplasm Formation and Viral Replication

Abstract

Rotaviruses are a major cause of acute gastroenteritis in infants and young children, producing a high burden of disease worldwide and over 600,000 deaths per annum, mainly in developing countries (43). Recently, two live attenuated rotavirus vaccines (49, 58) have been licensed in various countries, and their widespread use in universal mass vaccination programs is being implemented (55).Rotaviruses form a genus of the Reoviridae family. They contain a genome of 11 segments of double-stranded RNA (dsRNA) encoding six structural proteins (VP1, VP2, VP3, VP4, VP6, and VP7) and six nonstructural proteins (NSP1 to NSP6). After entry into the host cell the outer layer of the triple-layered particles (TLPs; infectious virions) is removed in endocytic vesicles, and the resulting double-layered particles (DLPs) actively transcribe mRNAs from the 11 RNA segments and release them into the cytoplasm. The mRNAs are translated into proteins but also act as templates for dsRNA synthesis (RNA replication). The early stages of viral morphogenesis and viral RNA replication occur in cytoplasmic inclusion bodies termed "viroplasms." Partially assembled DLPs are released from viroplasms and receive their outer layer in the rough endoplasmic reticulum (RER), forming TLPs (for details, see Estes and Kapikian [20]).The rotavirus nonstructural proteins NSP2 and NSP5 are major components of viroplasms (20, 47). These two proteins alone are sufficient to induce the formation of viroplasm-like structures (VLS) (21). Blocking of either NSP2 or NSP5 in rotavirus-infected cells significantly reduces viroplasm formation and the production of infectious viral progeny (11,54,57). Until now, host cell proteins involved in viroplasm formation have not been identified.Morphological similarities between viroplasms and lipid droplets (LDs) prompted us to investigate their relationship. Both structures have phosphoproteins (NSP5 and perilipin A, respectively) inserted on their surface in ringlike shapes (16,34). LDs are intracellular organelles involved in lipid and carbohydrate metabolism. They consist of a neutral lipid core surrounded by a phospholipid monolayer containing LD-associated proteins; those include proteins of the PAT family consisting of perilipin, adipophilin (adipose differentiation-related protein [ADRP]), and TIP-47 (9, 37). Lipolysis from LDs is regulated by hormones such as catecholamines, which trigger the phosphorylation of hormone-sensitive lipase (HSL) and perilipin A and induce LD fragmentation. Incubating adipocytes with the ␤-adrenergic agonist isoproterenol and the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX) activates this pathway (27, 34). LD formation can also be blocked

Who is the puppet master? Replication of a parasitic wasp-associated virus correlates with host behaviour manipulation

“…Interestingly, all positive-strand viruses rely on lipids to replicate, mostly from the organelle membrane but sometimes from lipid droplets [27]. For example, lipid droplets play a key role in hepatitis C virus and rotavirus replication [28,29]. Thus, DcPV may use lipid droplets in a similar way to replicate in the ladybeetle nervous tissues.…”

Inhibitory Effects of Bile Acids and Synthetic Farnesoid X Receptor Agonists on Rotavirus Replication

“…For example, cholesterol depletion by lovastatin, an inhibitor of cholesterol biosynthesis, was shown to reduce rotavirus replication in MA104 cells (31). Likewise, drugs that disperse lipid droplets by promoting lipolysis were shown to interfere with rotavirus particle or viroplasm formation (7). Therefore, lipid metabolism was suggested as a novel therapeutic target for rotavirus infections.…”

“…Previously, it was shown that disruption of lipid rafts and/or lipid droplets decreased infectious rotaviruses by inhibition of rotavirus morphogenesis (7,10). Lipid rafts are specialized membrane domains enriched in glycosphingolipids, cholesterol, and protein.…”

Forkhead Box Transcription Factor Regulation and Lipid Accumulation by Hepatitis C Virus

“…Rotaviruses associate with cellular lipid droplets for replication, and compounds disrupting lipid droplets inhibit rotavirus replication (39). Replication of another flavivirus, West Nile virus (WNV), is associated with intracellular membrane rearrangements and requires fatty acid synthesis (40).…”